1. Field of the Invention
The present invention relates to an image pickup device having an electronic zooming function of zooming in on an image (i.e., enlarging the image).
2. Description of Related Art
As an image pickup device having the electronic zooming function, there has provided a digital camera having an image zooming display function disclosed in patent reference 1. This digital camera can create a zoom-in display of a moving image, a static image, or a reproduced image which is displayed on a liquid crystal display when shooting. The digital camera uses a frame memory as a memory for display of images, and is provided with an image display device that can display a moving image, a desired image specifying unit for specifying a desired image, and an enlarged image displaying unit for enlarging the desired image specified by the desired image specifying unit and displaying the specified, desired image with a predetermined scaling factor on the image display device.
There has also been provided an image processing device disclosed by patent reference 2 as an image pickup device that implements an electronic zooming function by changing the sampling frequency of incoming image signals. The image processing device is provided with a charge-coupled image sensor, an analog signal processing unit, an A/D converter, an image memory as a frame buffer, a digital signal processing unit, a D/A converter, a monitor, a variable sampling clock generating unit, a system control unit, and a scaling-factor setting unit.
[Patent reference 1] Japanese patent application publication (TOKKAIEHI) No. 10-336494 (see paragraphs denoted by 0010, 0011, and 0016)
[Patent reference 2] Japanese patent application publication (TOKKAIEHI) No. 9-326957 (see paragraphs denoted by 0025, 0026, and 0028)
A problem with a prior art image pickup device constructed as mentioned above is that it has to be provided with a large amount of frame memory in order to keep the frame rate constant when performing electronic zooming, and this results in an increase in the power consumption of the image pickup device, an increase in the size of the image pickup device, and an increase in the cost of the image pickup device. In particular, it is difficult to apply the prior art image pickup device to equipment for mobile use.